The Panbo Forum

Arghhhhh... Radar Overlay.......

So I was trying to get one of the new Raymarine plotters to do radar overlay last night and no matter what kept getting "No Heading Data". For years I have set up Rayamrine, Garmin and other brands to do radar overlay by using the internal GPS heading data.... Well, not anymore..!!

It seems, according to an inside rep ar Raymarine, that one of Raymarine's competitors was sued because a customer hit something and blamed it on the "yaw" that you get between the radar, which is fixed to the vessel, and the yaw that the GPS sees where the land will move slightly behind the radar. The radar is on target, despite the plotter needing to catch up, but apparently someone still sued over this.

So my rep at Raymarine tells me everyone, Garmin, Simrad, Ray, Furuno, Lowrance etc. have all turned off the internal GPS as heading data for radar overlay because of this lawsuit? I would like to know what Ben or anyone else knows about this?

So now we have to use an external heading source such as a fluxgate as a heading sensor if we want to have radar overlay. All this thanks to some SCHMUCK and his LAWYER.

So I asked my rep what he thought the court case would look like when SCHMUCK B lays a bag of tools or another ferrous object next to his fluxgate and then bashes into something???? Hmmmm.... It is a lot harder to trick a GPS heading than it is to trick a fluxgate compass in most boats..

I recently had to move a frying pan in an adjacent locker and hand the customer a $125.00 bill to do so... How's that radar overlay with the frying pan next to it working out for you???

Arghhhhhhh......

Pretty soon we won't even have radar overlay if the SCHMUCKS and their LAWYERS have their way...

Try telling a customer who just laid out 4K on a new plotter, dome and radar pole that he now needs an autopilot or a NEMA 2000 fluxgate heading sensor on TOP OF the additional $300.00 in cabling and bus N2k/Seatalk Ng/Sea Talk HS to get his NEW Raymraine stuff just to talk to his OLD, yes last season is "OLD" Raymarine stuff........ But hey we boaters are rich right...

Oh and DO NOT upgrade older units to newer software!

So Ben any thruth to what my Raymarine rep told me? Have all companies really disabled radar overlay heading data from an internal GPS source????

-RC
Compass Marine Inc.

6 Replies

Well, RC, you are not the only tech to hear about this. Here's what a Florida installer writes:

"I had heard the radar overlay story from a Ray tech who told me about an accident that involved Furuno gear. Because of some issue, the chart had become skewed relative to the radar on the MFD (yawing?) and it resulted in alleged bad info for the helmsman and a collision. As a result Furuno, followed by Ray disabled overlay based on COG from the GPS. Ray did issue an update for the classic E's and C's to disable this function, and it doesn't exist for the new products. I'll be damned if I can find the story or lawsuit associated with it."

But it's my impression that doing radar overlay with COG instead of Heading has always been considered a bit dicey. Note the comments to this entry: http://goo.gl/mqmLT

This is getting confusing. My trustworthy source at Raymarine is looking for a definitive answer but so far this is what he thinks:

"On the overlay question, I need to get the official reason as to why we switched. For many years we did allow both overlay and MARPA to function without a compass of any kind. We did stipulate that for best performance a fast heading source (at 5 or 10 Hz) was strongly recommended. COG would power those features at speeds over 2 knots SOG. About a year ago they changed the code and now require a heading source for both of those features, though it does not have to be a fast update source. Any autopilot, electronic compass, or instrument on NMEA0183, SeaTalk, NMEA200/SeaTalk NG will suffice.

I think whoever the installer spoke with in our tech support had the overlay software change mixed up with the Honeywell lawsuit that Raymarine, Furuno, Navico and the rest of the gang are all dealing with. That being said though, I think the change was brought on more by European Union regulations than anything else."

When RC called me about this, I thought of the Honeywell suit too. More info on that here: http://goo.gl/COFsr

Chris Lapozza of Precision Marine posted a strong comment on this matter on the main blog and I'm moving it here:

"I read the post by the Compass Marine technician, as well as all responses. I would place this in the forum, but lost my password and forgot my username ten minutes after I signed up when it first was launched. So here I go.

Does anyone remember Raymarine's smart heading sensor for the Pathfinder and C-Series? The XX radars even had their own dedicated heading sensors. While those were meant primarily for mARPA functions, they also provided a much more accurate overlay on the Seatalk line of displays. Think about ARPA for a second, and how it is used to calculate relative and accurate data to prevent collisions. Who would use COG to calculate a target's relative bearing and CPA? Furuno has demanded 10HzNMEA or AD10 heading for radar overlay since before their original NavNet series debuted, by choice. AD10! They created their own data protocol just for heading, that should illustrate the importance of such a value in navigation. The reason I am making a stink, is inherently unsafe to rely on COG to accurately overlay a radar image on a chart, especially at slow speeds. Never did I fail to explain this fact to a client who lacked a heading source but had a radar/plotter combo that did not require fast heading for overlay. Ever sit at the dock on a boat with no heading and watch the boat icon spin around in circles on the plotter? While GPS can establish your position (relative to the position of the GEO sats being tracked by a single receiver), GNSS cannot by virtue of its own design establish your magnetic bearing. In my opinion, heading is the most important navigational value onboard a boat. As far as RC's arguments against the practicality of an onboard fluxgate compass, does he also advocate removing all magnetic compasses from the boat due to their sensitivity to ferrous metals? Any boater who is unaware that magnetic fields affect compasses don't belong in the water anyway. RC seems to be arguing to protect the stupid, save them $600, so they can rely on an inaccurate radar overlay. Maybe fluxgate compasses shouldn't be installed so close to a frying pan, or one could actually place the 'Compass Area - Warning' stickers that are provided with pilots and heading sensors so mistakes like that won't happen. A normal boater would immediately wonder why their heading isn't changing while they are turning, and why their boat icon is upside down or skewed in HU mode. And if RC thinks people are so incapable of being told "This is your electronic heading sensor, keep anything metal away from it" - then install a Satellite Compass. Problem solved, especially if one plans to take a trip to the North Pole.

Thank you Raymarine for requiring heading for overlay, people will be safer now."

Apparently Raymarine removed radar overlay with COG due to safety concerns but is planning to put it back in a future software update, though the new version will only work when your boat is doing over 2 knots.

I'm not sure enough thought went in to that decision. Imagine sailing into Charleston SC, and ducking into a shallow, off-channel area to avoid big ship traffic, only to lose overlay because you are doing four knots in a two knot current.

Q4.DRS Is GPS COG information allowed for Heading and ARPA capability?
No, while some competitor’s radar systems allow GPS COG for Heading and
ARPA functionality, Furuno believes that this capability is dangerous and not
reliable, especially for ARPA calculations. NN3D systems require actual Heading
information at appropriate data rates (10Hz) for these functions.

Q14.CON What type of Heading inputs are supported by NavNet 3D?
Only NMEA heading (NMEA0183 or MEA2000) can be connected to a NN3D MFD
or DRS. Furuno proprietary AD10 (4-wire Clock and Data) protocol is no longer
supported.
Heading input to NN3D will allow functions such as Radar Overlay, North Up in
Radar and heading stabilization to work correctly. The NMEA0183 heading refresh
rate needs to be 100ms (or faster) in order for the DRS ARPA to function! If the
DRS ARPA feature is not required, a refresh rate of heading information can be
200ms (5 times per second). NN3D will reject 0183 Heading Information if refresh
rate is limited to only once or twice per second. NMEA0183 heading can be
accepted on any NMEA port at a baud rate of 4800 or 38.4kbps. Heading coming
from NMEA2000 sensors will always be at the correct speed for ARPA function.